Top unloading silo unloaders are used to remove all forms of feed materials from tower silos. These materials include silage and haylage ranging from hard binding material, padded and interlocked fibrous material, to loose light and soft material. During the cold season in northern geographic areas, the material adjacent the silo wall becomes a hard frozen mass. This hard frozen material is cut up and chipped from the silo wall with power-driven wall cleaners located on the wall end of the unloader. Different types and densities of material stored in tower silos make it difficult to efficiently remove the material from the silos.
Top unloading silo unloaders have the greatest material removing efficiency when they are generally horizontally level or a small upwardly directed cone and move around the silo wall at a constant or even speed. Under these operating conditions, the gathering and the flow of material through the unloader is uniform and at maximum capacity. Uneven material flow and large bunches of material reduce capacity of the unloader and can plug the unloader.
Large diameter tower silos, 20 to 30 feet, require large silo unloaders with long collectors. These collectors handle a large volume of material which must be evenly fed into the impeller. Maintaining the collector in a selected operating position, as a horizontally level position or at a slight angle and driving the collector around the silo wall at an even speed is desirable to insure even feeding of the material so that a high volume of material can be efficiently handled by the unloader.
Prior top unloading silo unloaders have the outer ends of the collectors in engagement with the top of the material when the unloader is not operating. These unloaders have high starting torque because they are started under partial load. In very cold conditions, top unloaders can freeze up if they are not cleared of material.